rman: re-create control file wo/ losing backup metadata

I have to admit I thought that this is not possible
and it works only one way, meaning backup metadata can
find its way into the catalog upon "register database"
or "resync catalog", but not the other way around
(from the catalog to a control file)

Case#12 in Robert Freeman's book however describes
exactly that. The problem though is that I am unable
to reproduce it. Here are the steps:

re-create CF w/ changed attribute (in my case number
of datafiles)
4. Open a database (no resetlogs/noreselogs required
as there is no recovery)
5. Reconnect to the catalog, full resync --> at this
step CF supposedly gets populated w/ the backup
metadata because "When the catalog recognizes the
db_name and dbid of the target, it will check its own
records and compare them to the target database CF.
When it finds no records in the CF, it will update
them."

For some reason step 5 doesn't work for me (checked
via rman interface and CF dump level 10). What am I
missing?